We were actually at Epcot. We had decided to go to Magic Kingdom since they were having fireworks and Spectomagic that night. Eight out of our party of ten headed to the monorail station, we had just exited Spaceship Earth. We noticed that the sky had darkened considerably and it started to rain. My mother wanted to duck into a shop and stay there to wait. A woman nearby asked how long these showers usually last, and I said "It's Florida. Usually 20 minutes or so, then it passes."

We got our hands stamped for re-entry and the skies opened up. It started pouring. We ran for the monorail station, there was quite a bit of lightning. We queued up and waited for a while and no monorail came. After about 15 minutes a monorail could be seen slowly moving its way toward Epcot, but just as it got behind Spaceship Earth, there was a terrible flash of lightning, roar of thunder, and they lost power. The station operator came on and told us that they had just lost power on the entire Epcot grid. We waited some more, visibility was nothing. After a few minutes some rescue vehicles showed up, but after another ten minutes or so, they left. We were told that monorails probably would not be running for some time because this was a "particularly nasty storm system."
Everyone in the station had nowhere they could go. You couldn't go back out in the rain because it was coming down so hard.
It took another 30 or 40 minutes before the power came back up so they could get the monorail into the station, and when it did there was some applause. They were going to open the doors and at least let us sit down in the cars, but they lost power again! One of the castmembers was stuck in the car right in front of us for a few minutes. The emergency release wouldn't work from the inside. We got it open from the outside, and he said he was just happy not to be stuck in there anymore.
They manually opened all the doors and we went inside to sit down.
A woman next to us was on her cell phone talking to her cousin right there in Orlando, who then told us that we were under a tornado warning.
As soon as she said that, a castmember came over the loudspeaker and explained what the problems were with the power, that the storm included a tornado warning, and that they had to shut down all transportation services because of the storm. He said that as soon as they had power back up, they were going to test the monorail system using empty trains (he called the drivers guinea pigs) and once the storm abated somewhat, they were going to send out extra buses to help move guests.
We gave up and once the rain slowed a bit(it didn't stop until around 9pm) we left and went back to BCV to put on some dry clothes. We never did see the fireworks or Spectro on this trip.